A large number of malodorous molecules differing in polarity or molecular weight are found in our living environments. Various deodorization methods have been developed so far in order to deodorize these diverse malodorous molecules. In general, such deodorization methods are broadly classified into biological methods, chemical methods, physical methods, and sensory methods. Among the malodorous molecules, highly polar short-chain fatty acids or amines can be deodorized by the chemical method, i.e., neutralization reaction. Sulfur compounds such as thiol can be deodorized by the physical method, i.e., adsorption treatment. Still, there remain a large number of malodorous molecules which cannot be dealt with by the conventional deodorization methods. Also, the deodorization method based on adsorption treatment has a problem that it tends to cause the re-emission of a malodor. In addition, these conventional methods may mask even odors other than the malodor of interest. Thus, a deodorization method which can overcome these problems has been demanded.
Another known method involves deodorizing a malodor by providing another more strongly perceivable order using an aromatic. This method, however, may cause the unpleasant odor of the fragrance. In addition, when masking the malodor by using another odor from, for example, a perfume and an aromatic, an odorous substance which exhibits an effective deodorizing effect on the malodorous substance of interest must be searched. Heretofore, sensory tests by experts have been conducted for the evaluation of odors. Such sensory tests, however, present problems such as the need of fostering experts capable of evaluating odors and low throughputs. Thus, the previous search for an odorous substance which exhibits a deodorizing effect has not been easy to achieve.
In mammals such as humans, the olfactory sense works by the mechanism where odor molecules bind to olfactory receptors on olfactory nerve cells present in the olfactory epithelium lining the nasal cavity to transmit the responses of the receptors thereto to the central nervous system. In humans, approximately 400 olfactory receptors are reportedly found, and genes encoding these receptors account for approximately 3% of all human genes. In general, a set of olfactory receptors is associated with a set of odor molecules. This means that individual olfactory receptors can respond to a plurality of structurally similar odor molecules with different affinities, while individual odor molecules can be recognized by a plurality of olfactory receptors. According to another report, an odor molecule activating a certain olfactory receptor functions as an antagonist inhibiting the activation of a different olfactory receptor. These combined responses of a set of olfactory receptors provide perceivable individual odors.
Accordingly, when a certain odor molecule coexists with a different odor molecule, the different odor molecule may inhibit the response of a receptor corresponding to the certain odor molecule, resulting in the final perception of a different odor. Such a mechanism is called the antagonism of an olfactory receptor. The alteration of an odor caused by this receptor antagonism is a preferred deodorization approach because this approach, unlike the deodorization methods which involve adding an odorant, for example, a perfume and an aromatic, can specifically cancel the perception of a malodor and does not cause an unpleasant odor derived from such an aromatic.
Skin tanning agents (also called self-tanning agents or sunless tanning agents) are skin cosmetics which colors the skin. Mainly, dihydroxyacetone (DHA) is used alone or in combination with, for example, erythrulose as an ingredient which causes the skin color to turn brown. Such an ingredient reacts with the upper layer of the skin to color the skin brown. Although this coloring is believed to proceed through browning reaction, the details of a mechanism underlying this reaction have hardly been elucidated. The browning reaction is also called Maillard reaction in the field of food chemistry. This term refers to the reaction through which a nitrogen-containing compound such as an amino acid or a protein is polymerized with a reduced sugar to form a brown polymer called melanoidin. The Maillard reaction is involved in food coloring or aroma component formation caused by the heating, etc. of foods.
3-Hydroxy-4,5-dimethyl-2(5H)-furanone (sotolone) is a substance known to have an odor expressed as a “curry-like flavor”, a “caramel aroma”, “burnt sugar”, “burn”, “spicy”, etc. (Non-Patent Documents 1 to 4). Sotolone generally works as an off-flavor having an unpleasant smell similar to that of crude drugs at high concentrations, but produces a syrup-like aroma at low concentrations. Sotolone reportedly induces the response of an olfactory receptor OR8D1 (Non-Patent Document 5).